Process and apparatus for coating a tube of fiber material with viscose by extrusion

ABSTRACT

THIS INVENTION RELATES TO A PROCESS AND APPARATUS FOR THE CONTINUOUS COATING OF A TUBE OF FIBER MATERIALS WITH VISCOSE, THE PROCESS COMPRISING CONVEYING THE TUBE SO THAT ITS WALL TRAVERSES A CYLINDRICAL ZONE OF A WIDTH OF 0.3 TO 1.0 MM. DEFINED BY EXTERNAL AND INTERNAL ELEMENTS, AND IN ITS PROGRESS THROUGH SAID ZONE IS COATED WITH VISCOSE FIRST ON THE EXTERIOR AND THEN ON THE INTERIOR THEEREOF.

Jan. 9, 1973 E. KINDL ET AL PROCESS AND APPARATUS FOR COATING A TUBE 0FFIBER MATERIAL WITH VISCOSE BY EXTRUSION Filed Dec. 23. 1970 INVENTORSERWIN KINDL GUNTER GERIGK "United States Patent 3,709,720 PROCESS ANDAPPARATUS FOR COATING A TUBE OF FIBER MATERIAL WITH VISCOSE BY EXTRUSIONErwin Kindl, Weinfeldstrasse 17, Wiesbaden-Biebrich, Germany, and GunterGerigk, Wintersteinstrasse 6, Oberursel, Germany Filed Dec. 23, 1970,Ser. No. 100,916 Claims priority, application Germany, Dec. 27, 1969, P19 65 130.0 Int. Cl. B44d N16 US. Cl. 117-95 3 Claims ABSTRACT OF THEDISCLOSURE This invention relates to a process and apparatus for thecontinuous coating of a tube of fiber material with viscose, the processcomprising conveying the tube so that its wall traverses a cylindricalzone of a Width of 0.3 to 1.0 mm. defined by external and internalelements, and in its progress through said zone is coated with viscosefirst on the exterior and then on the interior thereof.

This invention relates to a process and apparatus for coating a tube offiber material with viscose by extrusion. Fiber-reinforced tubes ofregenerated cellulose are known which consist of a tube of fibermaterial coated on the outside and inside with a layer of regeneratedcellulose and which tube is filled more or less completely withregenerated cellulose located between the fibers. The tube of fibermaterial is formed from a web of fiber fleece by bonding together theoverlapped edges of the web. The seam is preferably bonded with viscose.The application of the two coatings of viscose is carried out with theaid of annular dies in conjunction with a backing element which supportsthe tube when the viscose is forced onto it from the annular dies. Whenapplying the outer coating, an annular die is employed which forces theviscose inwards and which surrounds the backing element, whereas whenthe inner coating is applied an annular die is used which forces theviscose outwards and is surrounded by an annular backing element. In US.Pats. Nos. 2,105,273 and 2,144,900 it is stated that the apparatusdescribed therein can be used for coating both sides of a tube. In oneof the above-mentioned patent specifications an annular die is describedsuitable for applying the outer coating of viscose, and the tube offiber material, directly after the application of the viscose, is passedthrough a cylindrical passage between the annular die and a backingelement. The tube, provided with the two coatings of viscose, is thensubjected to various further treatments having, among others, thepurposes of coagulating the viscose and regenerating it to formcellulose, washing the tube, incorporating a plasticizer into it, anddrying it.

In producing fiber-reinforced cellulose tubes by applying a coating ofviscose on only one side of the tube, it has been found expedient onlyto pass the tube into the setting bath, in which the viscose iscoagulated and regenerated partially or completely to form cellulose,after the viscose has fully penetrated the tube. If coagulation takesplace before the tube is fully penetrated by the viscose, then there isfinally obtained a fiber-reinforced cellulose tube of lower strength andpoorer transparency than is the case when coagulation and regenerationare carried out after complete saturation of the tube of fiber materialby the viscose.

The penetration of the viscose into the tube of fiber material requiresa certain time, as does the coagulation of the viscose in the settingbath. Since, during the continuous production of fiber-reinforced tubesof regenerated cellulose by the above-described method, the coating ofthe tube with viscose and the coagulation of the viscose coatings mustbe carried out while the tube is moving downwards, without being laidfiat, the height of the plant used increases with the requiredproduction rate and the length of time needed for the penetration of theviscose into the tube and for coagulation of the viscose.

The present invention provides a process for the continuous coating of atube of fiber material with viscose, wherein the tube is so conveyedthat its wall traverses a cylindrical passage of a width of 0.3 to 1.0mm, defined by external and internal elements, and in its progressthrough this passage is coated with viscose first on the exterior andthen on the interior. This process reduces the amount of space and timerequired for the coating of a tube of fiber material on both sides withviscose.

The invention further provides an apparatus for carrying out thisprocess, the apparatus including as an external element an annular slotdie with the slot directed internally toward the passage and as aninternal element an annular slot die with the slot directed externallytoward the passage, the arrangement being such that the passage has theindicated width and external and internal coating of the tube can becarried out in the indicated sequence. The distance from the exitopening of the passage through which the tube passes at which theviscose is applied to the inside of the tube depends upon the selectedwidth of the passage through which the tube pases. The distance isbetween 1 and 50 mm. and must be the greater the greater the width ofthe passage. The thinner the fiber fleece of which the tube is made, thegreater, as a rule, the width within the stated limits of 0.3 and 1.0mm. Advantageously, the following relationship are observed between thewidth w of the pasage through which the tube passes and the distance abetween the slot in the inner die and the exit opening (values in mm.)

The distance a is measured from the exit opening to the nearest edge ofthe annular slot in the inner die. Intermediate values between thoseshown in the above table of relationships can, of course, be used.

The same limits apply to the distance over which the tube is passedbetween the application of the viscose to its outside and theapplication to its inside. Here, if required, relatively short distancescan be used. The distance over which the tube is passed in the passageprior to the application of viscose to the outside of the tube is suchthat no viscose escapes 'at the entry opening of the passage throughwhich the tube passes. For this purpose, a distance of travel of atleast 2 mm. is generally necessary.

Advantageously, this distance is kept within the abovestated limits forthe distance a.

In the production of fiber-reinforced synthetic sausage casings made ofregerated cellulose for which the method is primarily intended, use ismade in most cases of fiber fleeces having a thickness of 0.06 to 0.12mm. The abovementioned and following details relating to dimensions suchas length and width of the passage through which the tube passes and thedistances of the slots in the annular dies from one another or from theentry or exit openings, respectively, of the passage through which thetube passes apply in the case of fiber fleeces of the above thicknesses.

In the process of the invention the viscose is expediently applied tothe inside of the tube of fiber material at the latest one second afterthe application of viscose to the outside of the tube, andadvantageously the two applicatrons of viscose take place with aninterval of 0.003 to 0.3 second. The rate at which the operation iscarried out, i.e. the rate of travel of the tube of fiber material, canbe 20 meters/min. or more. Generally, the passage through which the tubepasses 18 of the same width from the entry opening to the exit opening.The width may vary within the length of the passage but preferably anyvariation is at most 0.2 mm. However, the approach to the entry openingand the departure path from the exit opening may, if desired, beconvergent and divergent, respectively.

The apparatus of the invention is further illustrated diagrammaticallyby way of example in the accompanying drawing, the single figure ofwhich is a cross-section of the apparatus.

Referring to the drawing, the apparatus consists of an outer annular dieand an inner annular die located therein, each of the two diesconsisting of two parts, i.e. an upper part 1a and 11' respectively anda lower part 2a and 2i respectively.

The outer annular die 1a, 2a has a central cylindrical bore, the wall ofwhich is formed by an upper lip 3a and a lower lip 4a of the die. Thetwo component parts 1a and 2a of the die form an annular chamber 6a intowhich leads a feed pipe 5a. The annular chamber 6a is for receivingviscose which is forced into it through the feed pipe 5a. The viscosepasses from the annular chamber 6a into an annular slot 7a which entersthe cylindrical bore between the two lips 3a and 4a of the die.

The inner annular die 1i, 2i is located in the central bore of the outerannular die 1a, 2a. The outer walls of this inner die are formed by anupper lip 3i and a lower lip 4i of the inner die. The two componentparts 1i and 2i likewise form an annular chamber 6i.

A feed pipe 5i enters this chamber. The annular chamber 61' is also usedfor receiving viscose which is forced I into it through the feed pipe5i. The viscose passes from the annular chamber 6i into an annular slot7i which is formed between the lips 3i and 4i of the die and extendsthrough the outer wall of the annular die 1i, 2i.

Between the outer die lips 3a and 4a on the one hand and the inner dielips 3i and 4i on the other there is a cylindrical annular passage 8 bywhich the tube passes through the apparatus. Its entry opening isdesignated by the reference symbol 8e, and its exit opening by 8f. Theupper lip 3i of the inner annular die constitutes a backing element forthe outer annular die 1a, 2a, and the lower lip 4a of the outer annulardie 1a, at the same time constitutes a backing element for the innerannular die 1i, 2i.

The two annular dies 1a, 2a and 1i, 2i are secured to a common frame insuch a manner that they can be lined up coaxially with one another. Theframe, the means for securing the two annular dies to it and thecentering device are of known type and are not illustrated in thedrawing.

In the drawing, the tube of fiber material that is to be coated isdesignated by the numeral 9, and its overlapped seam by the numeral 10.

The values a and w referred to above can be easily related to theaccompanying drawing. Preferably, the distances between the entryopening of the passage for the tube and the annular slot of the externaldie and between the annular slot of the internal die and the exitopening of the passage for the tube are at least 2 mm. and at leastthree times the width of the passage. They are preferably 3 to 15 mm.and the width of the passage through which the tube passes is preferably0.4 to 0.8 mm. Preferably, none of the three distances referred to aboveis greater than mm. Greater distances would not bring about anyadditional advantages in the invention, but would cause the disadvantagethat more material would be used for constructing the apparatus and theapparatus would become unnecessarily long.

For widths w other than those given it is preferable to usecorresponding intermediate values for a, as indicated. The followingrelationship appears to apply, with good approximation to valuesobtained in practice, for the preferable minimum value of the distance ain relation to the width w (both measured in mm.):

a minimum value of 1 being used, however, if this equation results in asmaller distance. The following relationship seems to apply, with goodapproximation to values obtained in practice, for the preferred maximumvalue of the distance:

The annular slots in the two annular dies usually have a width of lessthan 1 mm., and their length, in the radial direction, is usually only afew millimeters, i.e. 2 to 3 mm. However, neither the width nor thelength of the annular slots 7a and 7i appears to have an appreciableeifect upon the maximum rate at which the tube of fiber material can becoated with viscose, without failure of the viscose to completelysaturate the tube or other undesirable effects occurring during theproduction of a fiber-reinforced cellulose tube. The amount of viscoseper unit area applied to the tube of fiber material depends upon thequantity of viscose which is forced through the annular slots (7a and7i) of the two dies during unit time, the rate of travel of the tubethrough the apparatus being the same. The total quantity of viscoseapplied can be distributed in widely varying proportions over theoutside and inside of the tube of fiber material.

The annular slots in the two dies are preferably directedperpendicularly to the passage through which the tube passes, but can,however, also extend toward it at a downwardly inclined angle.

The apparatus of the invention is suitable for coating with viscose bothsides of tubes of fiber material which are made from fiber fleeceshaving a thickness of approximately 0.06 to 0.12 mm. Tubes of fibermaterial having diameters of 30 mm. or more can be coated. There appearsto be no upper limit as regards diameter, since tubes of fiber materialof relatively large diameter-up to mm.have been successfully coatedusing the apparatus of the invention.

The method and apparatus of the invention enable viscose to be appliedsuccessively to the two sides of a tube of fiber material in arelatively short apparatus. The method and apparatus also offer theadvantage that the viscose applied to the tube of fiber material rapidlypenetrates into the tube. Thus, with a prescribed height of coatingapparatus, it is possible to carry out two-sided coating more rapidlythan previously, since the tube does not travel any great distancebetween the points at which the two layers of viscose are applied, andafter leaving the apparatus and to the point at which the viscose hasfully penetrated the tube, the latter has to travel through the air overonly a relatively short distance, so that the coagulating bath for theviscose can be made correspondingly deeper and the tube can be passedthrough it more rapidly. Conversely, it becomes possible to achieve aprescribed operating rate with coating equipment, the height of which isless than heretofore. The method and the apparatus also offer theadvantage that good results are obtained even when no separate step inthe method is used for bonding the overlapping edges of the fiberfleece, the bonding of the overlapped portions instead taking placeincidentally as a result of the external and internal coating of thetube of fiber material with viscose. The method is preferably performedin this manner, that is, without a separate operation for bonding theoverlapped seam.

The following examples further illustrate the invention:

EXAMPLE 1 For producing a fiber-reinforced cellulose casing coated onboth sides with cellulose, use was made of apparatus having thefollowing dimensions:

Inner die: Mm.

Outside diameter measured at the lips of the die 61.80 Thickness ofupper lip 10.0 Thickness of lower lip 9.0 Width of annular slot 0.30Length of annular slot (radial) 2.0 Outer die:

Inside diameter, measured at the lips of the die 3.20 Thickness of upperlip 4.0 Thickness of lower lip 15.0 Width of annular slot 0.30 Length ofannular slot (radial) 2.0

Mm. Width of passage through which tube passes 0.70 Length of passagethrough which tube passes 19.3

The annular slots in both dies were perpendicular to the passage throughwhich the tube passes.

The surface of the coagulating bath was at a distance of 50 cm. from theapparatus (travel through air). As a result of this short distance oftravel through the air, which was determined to enable the apparatus tobe operated in an improved manner, it was possible, in the same space asusual, to employ a three-meter high coagulating tank instead of thetwo-meter high tank previously used when applying a viscose coating onone side only of the tube. The distance of travel of the fiber fleececoated on both sides with viscose, from the point of entry into thecoagulating bath to a lower guide roller (where the tube is flattened)was 2.60 meters.

The coagulating bath contained 20 g./l. (gram per liter) of sulfuricacid and 150 g./l. of ammonium sulfate. The fiber fleece was a standardcommercial product as used in the manufacture of casings of fibermaterial and had a weight of 21 g. per square meter, a thickness of 0.09mm. and a width of 204 mm. Bonding of the overlapping strip of fleecewith viscose was not carried out as a separate step since this wasaccomplished incidentally by the viscose penetrating the fleece from theoutward and inward directions.

Under the conditions described above, and at a speed of passage of 22m./min. (meters per minute), a fiber casing (synthetic cellulose casingwith a fiber fleece base) of excellent appearance and very greatstrength was obtained. Furthermore, by using the apparatus described andby varying the quantities of viscose fed to the two annular nozzles, itwas possible to effect a wide variation of the amount of viscose appliedexternally and internally. For example, a fiber casing having a weightper square meter of 95 g. was produced, on which 50 percent of theviscose was applied from the inside and 50 percent from the outside.

6 EXAMPLE 2 For producing a fiber-reinforced cellulose casing coated onboth sides, use was made of apparatus having the following dimensions:

Inner die: Mm.

Outside diameter measured at the lips of the die 61.80

Thickness of upper lip 12.0

Thickness of lower lip 6.0

Width of annular slot 0.40

Length of annular slot (radial) 3.0

Outer die:

Inside diameter, measured at lips of the die 63.30

Thickness of upper lip 6.0 Thickness of lower lip 12.0 Width of annularslot 0.40 Length of annular slot (radial) 3.0

Width of passage through which tube passes 0.75 Length of passagethrough which tube passes 18.4

The annular slots in both dies were perpendicular to the passage throughwhich the tube passes.

The distance between the apparatus and the surface of the coagulatingbath was 50 cm., and the distance from the surface of this bath to alower guide roller (where the tube is flattened) was 2.60 m.

The coagulating bath contained 15 g./l. of sulfuric acid and g./ l. ofammonium sulfate. The fiber fleece had a weight per square meter of 17g., a thickness of 0.07 mm. and a width of 204 mm. 70 percent of theviscose was applied on the outside and 30 percent on the inside. At aspeed of passage of 20 m./min. a very transparent, parchment-like fibercasing of excellent strength was obtained.

In the above examples, the time required for the viscose to penetrateinto the fiber fleece was 1.5 sec. This time could be further reducedwithout adversely affecting the quality of the product.

It will be obvious to those skilled in the art that many modificationsmay be made within the scope of the present invention Without departingfrom the spirit thereof, and the invention includes all suchmodifications.

What is claimed is:

1. A process for the continuous coating of a tube of fiber material withviscose, which comprises conveying the tube so that its wall traverses acylindrical zone of a width of 0.3 to 1.0 -mm., defined by external andinternal elements, and in its progress through said zone is coated withviscose, by coating zones in said external and internal elements, firston the exterior and then on the interior thereof.

2. A process as claimed in claim 1 in which the internal coating ofviscose is applied, at the latest, 1 second after the application of theexternal coating of viscose.

3. A process as claimed in claim 1 in which the internal coating ofviscose is applied 0.003 to 0.3 second after the external coating.

References Cited UNITED STATES PATENTS 2,144,900 11/1939 Smith 117-95 X2,210,436 8/1940 Weinsang et al 1l7-95 X 2,767,431 10/1956 De Laubarede117-95 X EDWARD G. WHITBY, Primary Examiner U.S. Cl. X.R.

11794, 121, 166, DIG. 9; 118-405; 264188

